1. Field of the Invention
The present invention relates to hauling vehicles having frame-mounted cargo boxes and more particularly relates to structure for sling loading of such vehicles. A preferred embodiment of the present invention relates to a sling load portal including a selectively sealable opening in the bed of the cargo box of a utility vehicle.
2. Description of Related Art
Various hauling vehicle designs are known which include a cargo box having side walls and a tailgate which forms a rear wall thereof.
Utility vehicles such as the vehicle described herein are often adapted to be used in off-road conditions It is well known that such vehicles have also been modified for use in providing emergency medical treatment and transport. To position a utility vehicle in a particular off-road location (for example, to an area from which transportation of injured persons is required), it may be necessary or desirable to bring the vehicle there by a method other than its own power.
The sling load method of carrying vehicles ("sling loading") involves the rigging of the vehicle by fastening a sling comprising a set of sling legs (chains, cables, ropes or other straps) to multiple points about the vehicle, typically at or near comers of vehicle The sling legs are gathered at central point above vehicle from which the vehicle will be lifted. The sling is in turn fastened to a cargo hook attached to a piece of equipment such as a crane or aircraft such as a helicopter. Sling loading cargo and equipment overcomes many of the obstacles that hinder other modes of movement. In military operations in particular, helicopter sling loading is used extensively in the ship-to-shore movement of cargo and equipment during amphibious operations, movement of supplies and equipment over the battlefield, vertical replenishment of ships, and firepower emplacement. The advantages of the sling load method include the ability to bypass surface obstacles to effect the rapid relocation of supplies and equipment.
In order to lift a vehicle by sling loading, it is normally desirable to attach the sling to the sturdiest part of the vehicle, which is the frame. Accordingly, lift provisions such as pivotable rings, shackles, eyelets, lugs, and loops are commonly fastened to the frame, serving as a location for attaching a sling or other lifting mechanism (the lift provisions may also be used to tie the vehicle down to a platform or other surface).
Sling loading a utility vehicle having a cargo box is particularly problematic because the cargo boxes of such vehicles are typically substantially larger than the frame of the utility vehicle itself, so that the lift provisions attached to the frame are located beneath the cargo box. When sling legs are used to rig the vehicle for sling loading, they must pass over the tailgate or the sidewalls of the cargo box. As force is applied to lift the vehicle, the straps will have the tendency to pull the cargo box off the vehicle. Cargo boxes of utility vehicles in particular are designed for carrying weight within the box so that force is transferred downward to the vehicle frame upon which the box is mounted. Upward force on the box is typically resisted only by the shear strength of pivots (commonly two bolts) which allow the box to tilt for unloading. During sling loading, the straps will also tend to deform sidewalls or the tailgate of the cargo box. In addition, abrasion between the sling legs and the sides of the cargo box may remove the paint from the vehicle and possibly damage the sling legs.